Ignition apparatus



Nov. 26, 1940. A, DE HARD 2,223,013

IGNITION APPARATUS Original Filed April 4, 195a BY W?.&W

76. 2 ATTORNEY Patented Nov. 26, 1940 UNITED STATES PATENT OFFICE 2,223,013 IGNITION APPARATUS Albert W. De Chard, Sidney, N. Y., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Substitute for abandoned application Serial No.

199,751, April 4, 1938. This application February 25, 1939, Serial No. 258,515

16 Claims. (Cl. 123-169) This application is a substitute for abandoned In shell I a central electrode 1 having a discflpp ca i n e ia N fil April 4, 1938. like head portion 8 and a threaded spindle l is This invention relates to spark plugs of the securely imbedded in an insulating compound type wherein the high tension circuit is not only II, preferably composed of va. ceramic material 5 insulated but also shielded or screened to prewhich completely fills the shell I from the lower vent interference with the reception in adjacent side of head portion 9 to a plane adjacent the radio equipment. bottom-most part of base 3.

One object of the invention is to provide a Lining the walls of the spark plug are insulatnovel spark plug which consists of a minimum ing cigarettes I2 and I3 preferably made of mica. 10 number of parts so as to simplify manufacture. Cigarette I2 extends upwardly from the shoulder 10 Another object of the invention is to provide It in the enlarged bore of shell I to spun-over a novel spark plug which is simple in structure shoulder I5 and in extending upwardly it closely and relatively inexpensive to manufacture. adheres to the wall in order that there shall be A further object of the invention is to provide no air between the cigarette and the walls which a spark plug that lends itself to be manufacmight cause corona losses when the spark plug 15 tured in small sizes and more particularly to the is in use, and to prevent gas leakage. Cigarette manufacture of a 10 millimeter plug. I3 extends upwardly from ground electrode I6 Another object of the invention is to provide into the enlarged bore of shell I and while trava par plu t at s c pable f withstanding sudersing the bore of base portion 3 it also adheres den changes in temperature. in like manner as does mica cigarette I2 to the 20 A still further object of the invention is to prowalls. Vide a Spark plug which is bothmechanically Grounded electrode I5 is attached to base porand electrically strong, and is capable of long t 3 in any well known manner such as by service under severe service conditions. Silver ld in welding or spinning over. These a d ot o s w l appe m fully The grounded electrode is shown in the draw- 25 from a consideration of the detailed description ing as isc member with a single central openof the invention which follows. Although only ing through which the central electrode passes. Q Embodiment of the present invention is This embodiment is preferred since it decreases scribed illustrated in the accompanying the possibility of any particles of the insulating drawing to be expressly understood that this material falling into the combustion chamber of 30 drawing is for purposes of illustration only and the engma is not to be construed as a limitation of the scope Chamber n in the upper portion of the spark of invenmon' reference pmnam? bemg had plug is adapted to receive an ignition cable from for thls purpose to the appended chums a magneto or other high tension source. The

In the m wherein like reference charac' usual radio shield for the cable is tightly secured 35 ters refer to like parts throughout the several to the spark Plus by means of a coupling nut views.

. fastened to the threads 6.

1 is longltqdmal .sectional View of a The method of manufacturing the spark plug vice embodymg the mventlon; and is simple and requires a minimum number of 40 Fig. 2 is a transverse end, or bottom plan view operating steps 40 of the device of Fig. 1 showing one type of elec- I tmde design Unitary shell member I is made in any well known manner. The ark lu com rise unt l ber gi ghieldfilg i i 2 52552 3 Insulating cigarette I2 is inserted into enlarged upward extension of cylinder engaging base 3, upper portion of shell member I abutting against 45 there being an intermediate polygonal portion 4 shoulder I4 and extends close to the top of shield which receives the wrench or other tool for in- Mica cigarette is mselfted through sertion of the plug in th cylmder 11 the bottom of the shell I closely fitting the walls gaging base 3 has threads thereon to facilitate of base 3 and extending into upper Pomon securing the plug in the cylind r ll 0f an of the shell I. Central electrode I is then inserted 5 ternal combustion engine. Shielding element 2 through t e p of the Shell I until e owe is provided with cooling means in the form or tip of spindle 8 extends the proper distance below fins 5, and is also provided with a threaded porthe bottom of base 3. Head 9 of electrode 1 tion 6 which is to enable securing an ignition bears very tightly against mica cigarette I2. cable shield to the spark plug. After electrode I is inserted, the upper end of 55 shielding portion 2 is spun over forming a guard and holding means for mica cigarette I2.

Electrode 8 is held in position by means of a suitable tool while insulating compound II is inserted under pressure in a plastic state through the lower end of base 2 completely filling the space between the head 9 of electrode I and the lower end of base 3.

After the insertion of compound H the entire structure is baked to harden the insulating compound. After the hardening process insulating material H exerts a pressure against mica cigarettes l2 and I3 thereby giving a gas-tight fit to the spark plugs.

After the baking operation the proper amount of insulating material H is ground or shaved off so that the grounded electrode Hi can be permanently attached to base portion 3. Electrode i6 is preferably attached to base 3 by means of silver solder although other means can suitably be used.

While only one embodiment of the invention has been described and illustrated in the drawing, it will be apparent to those skilled in the art that the invention is capable of a wide variety of mechanical expressions, .while changes may be made in the form, details and proportions of the parts without departing from the spirit of the invention. Reference is to be had primarily to the appended claims for a definition of the limits or the invention.

What I claim is:

1. In a shielded spark plug comprising a unitary shell member having a bore therethrough the upper end of which is enlarged, the lower section of said shell member having threads thereon, a mica insulating cigarette positioned in said upper portion of said shell member and a second mica insulating cigarette extending into said upper portion from the lower end of said lower portion of the shell member, a central electrode having a head portion tightly fitting the first mentioned mica insulating cigarette and a threaded spindle extending from said enlarged bore to the lower end of said shell, and a ceramic insulator imbedding said electrode, the upper surface of said head portion and the tip portion of said electrode being free of said insulator.

2. In a spark plug comprising a unitary shell member having a bore therethrough, the upper end of said bore being enlarged, a mica insulating cigarette extending throughout the entire length of said enlarged part of said bore and a second mica insulating cigarette extending throughout the length of the lower portion of said bore partially into the enlarged bore, an elongated electrode in said bore, and a ceramic insulator filling the space between said electrode and said cigarettes.

3. In a spark plug a tubular body comprising a lower portion adapted to be mounted in the cylinder of an engine to be ignited and an upper portion of larger internal diameter adapted to receive a conductor cable, a tube of insulating material lining said upper portion, a tube of insulating material lining the lower portion and extending in overlapping relation with the first tube, a central electrode, and cementative insulating material filling the spaces between the tubes and electrode.

4. In a spark plug a tubular body comprising a lower portion adapted to be mounted in the cylinder of an internal combustion engine and an upper portion of larger internal diameter adapted to receive an ignition cable, a mica insulating cigarette lining said upper portion, a mica in sulating cigarette lining the lower portion and extending in overlapping relation with the first mica cigarette, a central electrode, and cementative insulating material filling the spaces between the cigarettes and electrode.

5. A spark plug comprising a shell having a bore therethrough with an enlarged upper portion and a reduced lower portion, insulating tubes lining the inner walls of the shell, one of said'insulating tubes lining the inner wall of the said upper enlarged portion and the other of said insulating tubes lining the inner wall of the reduced portion and extending into the enlarged upper portion, a central electrode with a head portion fixedly positioned in the enlarged upper portion and a threaded spindle extending downwardly from the head portion through the reduced portion, and a hardened insulating material completely filling said bore below the head of the central electrode.

6. A spark plug comprising a shell having a bore therethrough with an enlarged upper portion and a reduced lower portion, insulating tubes lining the inner walls of the shell, one of said insulating tubes lining the inner wall of the said upper enlarged portion and the other of said insulating tubes lining the inner wall of the reduced portion and extending into the enlarged upper portion, a central electrode with a head portion fixedly positioned in the enlarged upper portion and a threaded spindle extending downwardly from the head portion through the reduced portion, a hardened insulating material completely filling said bore below the head of the central electrode, a disc electrode attached to the lower extremity of the shell, surrounding the central electrode and bearing againstthe insulating material.

7. In a spark plug the combination of a finned body member having a double diameter bore therethrough, a central electrode with a disc-like head permanently positioned in the larger section of said shell and a spindle extending through the smaller section of said bore to a position near the lower extremity of said body, a second electrode member attached to the body member and surrounding the central electrode, and insulating means including a hardened ceramic insulating compound completely filling the space in said body between the disc head of the central electrode and the second electrode.

8. A spark plug comprising the combination of a shell body having a shield extension thereon, insulating sleeves lining the interior of said shell body and a central electrode element having a head and a spindle fixedly mounted in said shell, an insultor in the form of a. cementative material filling the shell member beneath the head of the central electrode member and around the spindle.

9. The method of manufacturing spark plugs which consists of the following steps: Inserting an insulating sleeve into one end of a spark plug shell, inserting a second insulating sleeve through the second end of said shell, inserting an electrode through said first end, forcing an insulating compound under pressure through the second end of said shell until the space surrounding the electrode in the shell is completely filled with the insulating compound, baking the entire structure until the insulating compound is hardened, and after the hardening process attaching a ground electrode to the shell.

10. The method of manufacturing spark plugs centrally of the bore in a spark plug shell, pressa portion of said bore with electrical insulating materials, placing an elongated electrode centrally of said bore, pressing an electrical insulating compound in a plastic state into said shell between said electrode and said insulating materials, and treating theentire asembly to harden the insulating compound.

12. The method of manufacturing spark plugs which comprises forming a tubular shell having a differential bore therethrough, lining each portion of said bore with a sleeve of electrical insulating material, the lining from one part of said bore extending into a larger part of said bore, placing an elongated electrode centrally of said bore, forcibly pressing an electrical insulating compound in a plastic state into said shell in the space between said electrode and said insulating sleeves, and baking the entire assembly to harden said insulating compound.

13. A spark plug comprising in combination a tubular body having ,a shield extension permanently fixed thereto and adapted to receive an ignition cable, insulating means lining the inner wall of said shield extension, an electrode centrally disposed in the bore of said body and having an enlarged head portion tightly engaging the inner wall of said lining and an electrical insulating compound substantially filling the bore of said body around said electrode.

14. In a spark plug, a tubular body having a differential bore therethrough, the portion of said bore having the larger internal diameter being adapted to receive an electrical conductor,

an electrode centrally disposed of said bore and extending into portions thereof having different internal diameters, and electrical insulating materials substantially filling the space-in said bore between the walls of the latter and said electrode.

15. In a spark plug, a tubular body member having a stepped bore therein, a central electrode having an enlarged portion permanently positioned in a part of said bore having the larger diameter and a spindle portion extending from said larger part of the bore through a smaller part of said bore, insulating material substantially filling the space in said body between the periphery of said electrode and the walls of said bore, and a ground electrode secured to said body for electrical cooperation with the end of said spindle.

16. In a spark plug, a tubular body comprising a lower portion and an upper portion of larger internal diameter than said lower portion. a tube of insulating material lining said upper portion, a tube of insulating material lining said lewer portion and extending into said upper portion, an electrode centrally disposed in said bore, and an electrical insulating material substantially filling the space in said body between said electrode and said tubes.

ALBERT W. DE CHARD. 

